There is a great post from Steve Laster in 2016 about optimizing ASP.NET Docker Image sizes. Since then Docker has added multi-stage build files so you can do more in one Dockerfile...which feels like one step even though it's not. Containers are about easy and reliable deployment, and they're also about density. You want to use as little memory as possible, sure, but it also is nice to make them as small as possible so you're not spending time moving them around the network. The size of the image file can also affect startup time for the container. Plus it's just tidy.